The present invention relates to video coding. More particularly, the present invention relates to a method for utilizing temporal prediction and motion compensated prediction to accomplish multiple description video coding.
Most of today""s video coder standards use block-based motion compensated prediction because of its success in achieving a good balance between coding efficiency and implementation complexity.
Multiple Description Coding (xe2x80x9cMDCxe2x80x9d) is a source coding method that increases the reliability of a communication system by decomposing a source into multiple bitstreams and then transmitting the bitstreams over separate, independent channels. An MDC system is designed so that, if all channels are received, a very good reconstruction can be made. However, if some channels are not received, a reasonably good reconstruction can still be obtained. In commonly assigned U.S. patent application Ser. No. 08/179,416, a generic method for MDC using a pairwise correlating transform referred to as (xe2x80x9cMDTCxe2x80x9d) is described. This generic method is designed by assuming the inputs are a set of Gaussian random variables. A method for applying this method for image coding is also described. A subsequent and similarly commonly assigned U.S. Provisional Application Ser. No. 60/145,937, describes a generalized MDTC method. Papers describing MDC-related work include: Y. Wang et al., xe2x80x9cMultiple Description Image Coding for Noisy Channels by Pairing Transform Coefficients,xe2x80x9d in Proc. IEEE 1997 First Workshop on Multimedia Signal Processing, (Princeton, N.J.), June, 1997; M. T. Orchard et al., xe2x80x9cRedundancy Rate Distortion Analysis of Multiple Description Image Coding Using Pairwise Correlating Transforms,xe2x80x9d in Proc. ICIP97, (Santa Barbara, Calif.), October, 1997; Y. Wang et al., xe2x80x9cOptimal Pairwise Correlating Transforms for Multiple Description Coding,xe2x80x9d in Proc. ICIP98, (Chicago, Ill.), October 1998; and V. A. Vaishampayan, xe2x80x9cDesign of Multiple Description Scalar Quantizer,xe2x80x9d in IEEE Trans. Inform. Theory, vol. 39, pp. 821-834, May 1993.
Unfortunately, in existing video coding systems when not all of the bitstream data sent over the separate channels is received, the quality of the reconstructed video sequence suffers. Likewise, as the amount of the bitstream data that is not received increases the quality of the reconstructed video sequence that can be obtained from the received bitstream decreases rapidly.
Accordingly, there is a need in the art for a new approach for coding a video sequence into two descriptions using temporal prediction and motion compensated prediction to improve the quality of the reconstructions that can be achieved when only one of the two descriptions is received.
Embodiments of the present invention provide a block-based motion-compensated predictive coding framework for realizing MDC, which includes two working modes: Intraframe Mode (I-mode) and Prediction Mode (P-mode). Coding in the P-mode involves the coding of the prediction errors and estimation/coding of motion. In addition, for both the I-mode and P-mode, the MDTC scheme has been adapted to code a block of Discrete Cosine Transform (xe2x80x9cDCTxe2x80x9d) coefficients.
Embodiments of the present invention provide a system and method for encoding a sequence of video frames. The system and method receive the sequence of video frames and then divide each video frame into a plurality of macroblocks. Each macroblock is then encoded using at least one of the I-mode technique and the P-mode technique, where, for n channels the prediction mode technique generates at least n+1 prediction error signals for each block. The system and method then provide the I-mode technique encoded data and the at least n+1 P-mode technique prediction error signals divided between each of the n channels being used to transmit the encoded video frame data.